Many occasions arise in which it is desired to apply a covering to the skin for therapeutic purposes. In the case of intact skin it may be desirable to apply a coating which contains a therapeutic agent to be taken up by the skin. A coating on intact skin also may serve to protect an area of skin against physical forces: abrasion or compression, for example. Injured or unhealthy skin requires coverings for therapy and protection, as well. Burns, wounds, ulcers and debilitated areas and skin-graft donor sites benefit from the delivery of therapeutic agents, the exclusion of ambient bacteria, the prevention of water loss, physical protection, and the preclusion of local accumulation of tissue fluids at the skin surface.
Objectives of this kind are met to some degree by bandages, foils or sheet material, either uniform or composite in structure, held in place by tying or adhesives. More intimate contact and easier application is achieved with creams or ointments, but these suffer from impermanence. Dissatisfaction with such skin coverings has stimulated search and invention of improved skin coverings of broad or specific utility. Many kinds of skin coverings suggested or investigated for utility are described by G. B. Park, Biomat. Med. Dev., Art. Org. 6 (1) 1-35 (1978). Although some skin covering materials have evolved through intuitive or empirical effort, most modern investigators are guided by recognition that there is need to meet such requirements as repeatable fabrication from available materials of appropriate costs, biocompatibility (including lack of antigenicity), ready conformability to the contours of the skin, adequate physical integrity, compatibility and lack of reactivity with pharmacological agents, regulated properties of water vapor transmission, capable of being rendered sterile or treatable in such a way so as not to constitute a bacterial host, suitable physical properties, e.g., elasticity, abrasion resistance, and strength, adherence to intact or injured skin, and in some instances, more narrowly specified properties. Despite improvements and advances in the technology, ideal or universally applicable systems have not yet been offered.
Although synthetic polymeric substances have played a part in providing materials for skin coverings, shortcomings persist. It will be apparent to those active in the fields of medicine, chemistry, and bioengineering, however, that the opportunity exists to discover polymeric substances meeting the perceived needs. A specially promising area of investigation is the chemical alteration of polymers known already to be biocompatible.